1. Field:
The present invention relates to structures adapted to protect grass seeded areas. More particularly, the new structure is an assembly of traction grids made interconnectable to form a pathway over grassy areas. Specifically, the invention is directed to a method of protecting grass which is subject to high levels of human or vehicular traffic, while simultaneously providing a traction surface for that traffic.
2. State of the Art:
The landscaping industry has long encountered the problem of providing walkways or pathways over grass seeded areas.
Typical varieties of grass, though somewhat resistent to the pounding and abrasion produced by traffic, are not sufficiently durable to withstand such continued abuse over extended periods. This vulnerability to damage in part results from the physical structure of the grass. The root structure of grass is concentrated near the soil surface. As a result, relatively small force applications can dislodge and destroy the roots. The green blade portion, though resilient, is relatively fragile and hence susceptible to serious damage should it be subjected to repeated abrasion or pounding.
Contemporary landscaping, whether in a commercial setting, e.g., parks, golf courses, or in a residential environment, often utilizes grass as an integral component of any design. Not only are lawns typically less burdensome in maintenance than other horticultural displays, e.g. flower gardens, but a wide expanse of uninterrupted grass is considered very attractive in an aesthetic sense.
As a general rule, grass use is found in areas where human or vehicular traffic is also present. The need, therefore, arises to provide grassy areas adapted to tolerate traffic while simultaneously retaining the aesthetic qualities inherent in grass seeded areas. Contemporary practice generally involves the construction of cement sidewalks, stone paths or ceramic tile walkways to address this need. Graveled walkways have also been used in some environments.
The use of these materials introduces a new series of problems. Not only are these materials expensive, they are burdensome to install and often require replacement. Furthermore, the use of these materials restricts the landscape engineer's attempt to imitate the aesthetic qualities found in natural settings. Moreover, these walkways complicate the task of mowing the grass. Oftimes the blades of the lawn mower are damaged from either hitting the walkways or ingesting gravel. In applications involving extensive pathways, such as parks, golf courses and jogging paths, the expense associated with installing and maintaining these types of pathways becomes cost prohibitive. The landscape designer is either required to sacrifice the beauty of unmarred grassy areas for a maze of cement or concrete sidewalks or alternately forego the sidewalks in favor of tolerating worn pathways.
The provision of a traction-yielding path surface has received some technical attention. In U.S. Pat. No. 964,601 (Akerson) a portable track for use in assisting automobiles and similar vehicles is disclosed. Akerson teaches the use of an assemblage of fabric, preferably canvas, which is securely stitched together to form a flexible path structure. The structure has a top surface possessing a high coefficient of friction. The fabric assembly, being essentially nonporous, is nonconducive to long term placement over a grassy surface. Not only would the grass covered by the mat be damaged for lack of sunlight, the relatively slick nature of the blade portion of the grass would fail to secure the mat. A force component directed to the mat parallel to the ground, as would typically be the case in the motion of a wheeled vehicle, would dislodge the mat. The provision of a traction surface for the vehicle would therefore be frustrated.
U.S. Pat. No. 3,836,075 to Botbol teaches the use of a cleated mat having means therein to interconnect a plurality of such mats to form a path. Similar to Akerson in its requirement of a nonporous base structure, Botbol's mat structure would create similar problems to those engendered by Akerson if placed over grass.
A grid-like mat intended for use over hard surface areas such as asphalt or concrete is manufactured and sold under the trademark "Duragrid" by Duragrid, Inc. of Salt Lake City, Utah, a subsidiary of Sport Court of America, Inc. of Midvale, Utah. The "Duragrid" mat consists of a lattice-like structure having a series of square apertures averaging approximately one quarter square inch in area. The "Duragrid" mat is adapted for renovating hard surfaces which have weathered or deteriorated. The use of this structure over grassy surfaces is counter producproductive because of the restricted size of the lattice apertures. The small apertures don't permit sufficient light and circulation to promote grass growth. Downwardly directed forces as provided by traffic eventually submerge the "Duragrid" mat into the soil, thereby nullifying any grass protective attributes of the grid. Traction mats for assisting in dislodging automobiles from snow, ice and similar obstacles are disclosed in U.S. Pat. No. 3,786,989 (Haynes); U.S. Pat. No. 4,061,268 (Demaster); and U.S. Pat. No. 2,577,890 (Hardy).